In the late 70s, I sometimes met my father in the cafe there. It was busy but you could get a really good hot salt beef sandwich and the coffee was good in an era before coffee shops (where largely the coffee isn't good)
When I was a child I can remember my Grannie saying Selfridges was gauche and pitched for north London.
Coming to London as an adult in the early 80s it seemed dated and chaotic. In the early 90s I whizzed in to have a squint at their bridal section and it was awful - scant in fact.
In my youth I much preferred Liberty, Dickens & Jones and Harvey Nicks for clothes; Harrods and JL for furniture.
I think I ventured into Selfridges in the mid 2000s. It was awful - stuffed with bling for WAGs and foreign money. I haven't set foot in there since but neither have I bothered with Harrods much since Fayed took over and rescinded a free trip to the bogs, otherwise £1, for account holders.
The department stores in London are fading. Where once we had: DH Evans, Dickens & Jones, Bourne & Hollingsworth (always a bit crap), Swann & Edgar, Simpsons, Marshall & Snelgrove we now have the Trocadero Centre, and largely fast food and crud. It's an entirely different landscape. Oxford Street is not a place I wish to venture. If I have to be in the West End, I get off it asap and am inclined to use the back entrance to the M&S Pantheon, venture to Liberty and walk down Regent Street to Piccadilly.
Much of Selfridges problem is that Oxford Street has lost its lure.